(Delphi DLL) Decrypt S/MIME and Verify S/MIME Signatures

Delphi DLL example to decrypt S/MIME and verify S/MIME signatures. The S/MIME is unwrapped to get the original MIME prior to signing/encrypting.

Chilkat for Delphi Downloads Chilkat non-ActiveX DLL for Delphi Chilkat ActiveX DLL for Delphi * The examples here use the non-ActiveX DLL.

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Cert, Mime;

...

procedure TForm1.Button1Click(Sender: TObject);
var
mime: HCkMime;
success: Boolean;
isEncrypted: Boolean;
isSigned: Boolean;
signerCert: HCkCert;
encryptCert: HCkCert;

begin
mime := CkMime_Create();

//  Any string argument automatically begins the 30-day trial.
success := CkMime_UnlockComponent(mime,'30-day trial');
if (success <> True) then
  begin
    Memo1.Lines.Add(CkMime__lastErrorText(mime));
    Exit;
  end;

//  Load an S/MIME message from a file:
success := CkMime_LoadMimeFile(mime,'signedMime.txt');
if (success <> True) then
  begin
    Memo1.Lines.Add(CkMime__lastErrorText(mime));
    Exit;
  end;

//  The ContainsEncryptedParts/ContainsSignedParts methods
//  can be called to determine if the MIME is encrypted and/or signed:
isEncrypted := CkMime_ContainsEncryptedParts(mime);
isSigned := CkMime_ContainsSignedParts(mime);

//  We don't want the "unwrap extras".  You'll see what those
//  are in a few moments...
CkMime_putUnwrapExtras(mime,False);

//  To verify the signature, call UnwrapSecurity.  This will
//  verify the signature(s) and decrypt the S/MIME and restore
//  the MIME to the unsigned/unencrypted state.
//  The results of what was found are present in the MIME object's
//  properties, as well as extra header fields that are added
//  to the unwrapped MIME.
success := CkMime_UnwrapSecurity(mime);
if (success <> True) then
  begin
    //  UnwrapSecurity returns True if all signatures were
    //  verified and all parts decrypted.
    Memo1.Lines.Add(CkMime__lastErrorText(mime));
    Exit;
  end;

//  The mime.UnwrapExtras property controls whether or not
//  these additional fields are added to the unwrapped MIME:
// 
//  X-NumPartsSigned: 1
//  X-SignaturesValid: yes
//  X-NumPartsEncrypted: 1
//  X-Decrypted: no
// 
//  The X-NumPartsSigned/X-SignaturesValid headers are added
//  if the MIME was signed.
// 
//  The X-NumPartsEncrypted/X-Decrypted headers are added
//  if the MIME was encrypted.
// 

//  If the MIME was signed, get the certificate used for signing.
if (isSigned = True) then
  begin
    //  The NumSignerCerts property indicates how many certificates
    //  were used for signing.  This example will assume the value is 1.
    //  To get the 1st signer cert, call GetSignerCert with an index of 0:

    signerCert := CkMime_GetSignerCert(mime,0);
    if (not (signerCert = nil )) then
      begin
        Memo1.Lines.Add('**** Signer Cert: ' + CkCert__subjectCN(signerCert));
      end;
  end;

//  If the MIME was encrypted, get the certificate used for encryption:
if (isEncrypted = True) then
  begin
    //  The NumEncryptCerts property indicates how many certificates
    //  were used for encrypting.  This example will assume the value is 1.
    //  To get the 1st encrypt cert, call GetEncryptCert with an index of 0:

    encryptCert := CkMime_GetEncryptCert(mime,0);
    if (not (encryptCert = nil )) then
      begin
        Memo1.Lines.Add('**** Encrypt Cert: ' + CkCert__subjectCN(encryptCert));
      end;
  end;

//  Display the unwrapped MIME:
Memo1.Lines.Add(CkMime__getMime(mime));

//  Save the unwrapped MIME to a file:
success := CkMime_SaveMime(mime,'unwrappedMime.txt');

CkMime_Dispose(mime);

end;